Subcutaneous Layer

The first layer below the cutaneous membrane is called the subcutaneous layer. It is also known as the hypodermis and superficial fascia. Although this layer helps stabilize the integumentary system and shares some characteristics, it is not technically a part of the integumentary system.

Within the subcutaneous layer, you can find major blood vessels, adipose tissue, connective tissue, lymphatic vessels, nerves, and glands.

The function of the hypodermis layer is to protect vital organs that are deeper in your body. The hypodermis is also heavily affected based on your sex and the hormones you produce. An increased concentration creates a hypodermis that is thicker in areas like the back, arms, and shoulders. If you have a higher concentration of estrogen then you can expect the hypodermis to be thicker in the butt, thighs, and hips.

The hypodermis is also a well-known area for medical injections. Things such as the hypodermic needle and subcutaneous injections target this area for the contents within this layer.


Layers Of The Dermis

The dermis layer is located inferior to the epidermis layer in the cutaneous layer. This layer is made of connective tissue and can be divided into two layers:

  1. Papillary Layer
  2. Reticular Layer

The papillary layer of the dermis is the most superficial layer of the two. It is inferior to the epidermis and superior to the Reticular layer. Within the papillary layer there are:

  • Dermal Papillae
  • Axons of Neurons
  • Loose Connective Tissue
  • Capillaries

This layer’s main function is to provide attachment to the epidermis layer but, it also provides nutrients through capillaries and sense through neurons.

The reticular layer of the dermis is inferior to the papillary layer and superficial to the subcutaneous layer. This layer consists of:

  • Sebaceous Glands
  • Hair Follicles
  • Networks of Dense Irregular Connective Tissue
  • Sweat Glands

The dermis layer functions to provide structure and integrity to the dermis layer. The networks of dense irregular tissue results in strong and elastic tissue within the skin. It also houses and supports accessory structures such as hair follicles and vital glands.

Organization Of The Dermis

Within the dermis, two major fibers contribute to the structure and organization of your skin. Collagen fibers are responsible for providing tensile strength to the skin or the resistance of something to break under tension. Elastic fibers are responsible for providing elasticity to the skin. Not only does it allow the skin to be elastic, but it also allows your skin to return to its original shape. Bother of these fibers can be seen in use when you stretch the skin on any part of your body.

So, if there are fibers responsible for keeping your skin strong and not distorted, why do we get wrinkles? Wrinkles can be attributed to three major factors:

  1. Age
  2. UV light
  3. Hormones

As a person gets older, their body begins to slow down and produce less of the essential materials needed for good health. One of the things the body reduces in producing as you get older is natural oils that keep your skin moisturized and elastic. Thus, with a decreased amount of oil that helps keep elastic fibers and collagen fibers healthy, your skin will become weaker and form wrinkles.

UV light is directly responsible for the majority of the damage that is caused to the dermis layer. UV light will penetrate the skin and damage collagen fibers. As a result of damaged collagen fibers, elastic fibers will have an increased chance of being produced abnormally. This creates wrinkles in the skin.

Hormones, believe it or not, play a role in the development of wrinkles and the overall health of your skin. One of the major hormones that have been linked to wrinkles being formed is estrogen. A decrease in estrogen can trigger an increased deterioration of elastic fibers in the dermis.

Stretch Marks

Stretch marks can be caused by large amounts of growth in a short period or over-stretching of the skin. This can be done during a growth spirt of puberty, pregnancy, and obesity. When this overstretching happens, the reticular fibers that are holding the layers of skin together break. These fibers do not recoil and do not return to normal after this. Instead, these broken fibers create wrinkles, creases, and stretch marks.

Tension Lines

Tensions lines, also known as cleavage lines, are patterns of collagen fibers that are made within the dermis. Since collagen fibers and elastic fibers usually organize themselves in a parallel pattern, the body has a grid of tension lines that is used heavily in the medical field. These patterns are formed from the mechanical stress of the body. Areas that need more structural support will have tension lines pulling on them in a certain direction.

These tension lines are used heavily in the medical field to avoid the formation of scars. Cutting perpendicular to these tension lines increases the risk of scarring on the body. Thus, surgeons will cut parallel to these lines to make the recovery of the patient as easy as possible. The reason for this is that cutting a tension line perpendicular causes more stress and damage to the fibers than if you cut parallel.

Blood Supply To The Skin

Within the skin, there are two major networks of arteries, veins, and smaller blood vessels. These networks form a plexus or a network of interconnecting blood vessels:

  1. Cutaneous Plexus
  2. Subpapillary Plexus

The cutaneous plexus is composed of arteries and veins. This network supplies the hypodermis, hair follicles, fatty tissue, glands, and deep areas of the dermis. This network is about 1.5 mm from the surface of your skin.

The subpapillary plexus is made of smaller blood vessels. It is located below the dermal papillae and superficial areas of the dermis. Within each dermal papilla, there is a capillary loop that helps supply blood to those areas of the skin.

Both the cutaneous plexus and the subpapillary plexus are direct contributors to thermoregulation or the ability to control the temperature of your body using the cardiovascular system. When the surrounding environment is hot and the body temperature is too high, the vessels will dilate to allow more blood flow to the surface. This helps dissipate some of the heat that is trapped in the body. When it is too cold, the vessels will constrict and focus blood on vital parts of the body such as the heart, lungs, and internal organs.

Nerve Supply To The Skin

The integumentary system is a vital part of sensing the surrounding area. The nerves that are embedded inside our skin can tell us if it is hot, cold, windy, rainy, if you are in pain, and so much more. Most of these senses are sent back to the central nervous system where the body will decide on how to maintain homeostasis.

As well as sensing the surrounding area, the nervous system is responsible for adjusting secretion rates and controlling the flow of blood.